Propeller pumps with axially and semi-axially arranged propeller blades are preferably used, for example, to transport large quantities of water to small or medium heights. These pumps are used for surface drainage, in sewage systems, high-water pumping stations, and the like. These applications frequently present the problem of accounting for varying or different intake quantities and intake heights. The same holds true for turbine units Used to generate power. Variable-pitch propellers are used so that the turbo-engine can be operated under these different conditions in the range of its maximum efficiency. The individual blades can thus be adjusted during operation in dependence on the intake conditions. The adjustment mechanism for the variable-pitch propellers is driven directly or indirectly by an electric motor or by a hydraulic system. Adjustment mechanisms to vary the blades are known for the variable-pitch propellers themselves.
The German reference DE-PS 694 029 discloses an adjustment device of this type. The adjustment device includes a shaft with a variable-pitch propeller fastened thereon, hydraulic transmission elements within the shaft, and a transmission dement for feeding hydraulic fluid into the shaft. The high-energy hydraulic fluid is supplied from an external source. The hydraulic fluid acts on an adjustment mechanism, here designated as a motor, within the propeller. The feeding transmission element is a disadvantage of this solution, since leaks can cause hydraulic fluid to reach the environment.